Don't do it to native. I recommend you to copy native to another folder. Edit module_info.py of the module system this package has and set the export dir like this example :
export_dir="D:/Games/MnB Warband/Modules/Copy of Native/"
Run the build_module.bat, and you can play Copy of Native module with custom banner enabled.
If you experience python related problem, just read Lumos' tutorial on my signature.